<%@ page import="java.util.ArrayList" %>
<%@ page import="java.util.List" %><%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2022-04-27
  Time: 11:43
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--%>
<%@ page contentType="text/html;charset=UTF-8" isELIgnored="false" language="java" %>
<html>
<head>
    <title>Title</title>
    <%
        request.setAttribute("a", -2);
        List list = new ArrayList<>();
        list.add(1);
        request.setAttribute("list", list);
        Object o = null;

        request.setAttribute("o",o);
    %>
</head>
<body>
  1.算数运算符： + - *  / %(mod)
 <br> ${2 mod 3}
    <br>
    2.关系运算: < > <= >= != ==
    ${5 gt 3}
    <br> 3.逻辑运算 && || ！
    ${1<2  and  2>1}
<br>4. 求值  三目 ？：
    ${a>0?a:-a}
   <br> 5.空运算 判断是不是null 集合是不是size=0  empty<br>
    list: ${empty list}<br> o: ${empty o}
    <br>6 .   .(引用属性)  [int] 下标 ，['name'] key

</body>
</html>
